Despite continuing improvements in the fuel efficiency of and reduction in undesirable operating emissions therefrom, modern fuel-fired water heaters still have various operational characteristics which are less than entirely satisfactory. For example, the burner pilots in most if not all conventional fuel-fired water heaters draw their combustion air from the area within the combustion chamber surrounding the pilot burner and its associated main burner. In some water heater combustion chamber configurations this air surrounding the pilot is diluted with exhaust gases. This undesirably reduces the amount of available oxygen for proper pilot combustion.
Another design challenge associated with modern fuel-fired water heaters is that the operating conditions can vary among the facility installations. That is, the fuel supply pressure for the igniter may vary from installation to installation, causing different combustion characteristics.